TM 5-3810-307-24-1-2
Piston. (Refer to Figure K-22.)
The piston is normally removed to inspect and to remove, inspect, rotate, and/or replace the piston
compression rings.
Removal.
a.
Remove the catch ring cap from the upper cylinder and set aside (Page K-52).
b.
If necessary, remove the piston transportation pin (1, Figure K-22) and the
intake/exhaust port weather cap (2). Install the trip transport bolt (3) in the hammer trip
assembly to secure in position on the hammer trip track rails.
c.
Remove the four lower cylinder (impact block) lubrication fittings (4) from the lower
cylinder.
d.
Screw the piston lifting eyebolt (5), stored in the tool box, into the top of the piston (6) to
full thread depth and tighten lock nut (7) to piston surface.
e.
With a lifting device and sling attached to the impact hammer, lift the impact hammer into
a vertical position and support.
f.
With a lifting device and sling attached to the piston lifting eyebolt (5), lift the piston (6)
out of the upper cylinder so that the piston (6) is clear of the cylinder. Carefully lower
piston (6) down to a horizontal position and place onto clean wood blocks. Maintain
cleanliness of piston (6). Also use blocks to support piston (6) from any sideways
movement.
CAUTION
Be careful not to deform (oversize or stretch) the compression rings
during removal, open just enough to slide compression ring over the
diameter of the piston.
g.
Using the piston ring pliers stored in the tool box, remove the piston compression rings
(8) from the piston (6).
Inspection.
a.
Inspect the nose of the piston (6, Figure K-22) for excess pitting, mushrooming, or
cracks.
b.
Inspect the piston (6) for evidence of exhaust smoke (blow-by) escaping as indicated by
an area of black carbon on the piston (as opposed to a shiny, well-lubricated piston).
This would indicate defective piston compression rings (8).
c.
Inspect the piston compression rings (8) for seizure in the grooves, wear, and sharp
edges or scoring marks.
d.
Place the piston compression rings (8) in the bore of the upper cylinder and measure the
piston compression ring gap with feeler gauges (i.e. the gap between the ends). The
piston compression ring gap should be between 0.09 0.11 inches (2.29-2.79 mm).
NOTE
Under normal wear conditions, only the first two piston compression rings
closest to the end of the piston require replacement.
Change-1 K-53
